Traditional methods of making a homologous series of compounds, or the testing of new potential drug compounds comprising a series of like compounds, has been a slow process because each member of the series or each potential drug must be made individually and tested individually. For example, a plurality of potential drug compounds is tested by using an agent to test a plurality of materials that differ perhaps only by a single amino acid or nucleotide base, or have a different sequence of amino acids or nucleotides.
Recently the process has been improved somewhat by combining the synthesis of various compounds having potential biological activity, for example, and traditional semiconductor techniques. A semiconductor or dielectric substrate for example is coated with a biologic precursor having amino groups with a light-sensitive protective chemical attached thereto, and a series of masks are placed over the substrate, each mask having an opening. A coupling agent, such as a photosensitive amino acid, is illuminated through the opening, forming a particular compound by reaction with the amino compound. Additional masks are used with different coupling agents to form an array of different peptides on the substrate which array can then be tested for biologic activity. Suitably this is done by exposure of the array to a target molecule, such as an antibody or a virus. The array is exposed to a biologic receptor having a fluorescent tag, and the whole array is incubated with the receptor. If the receptor binds to any compound in the array, the site of the fluorescent tag can be detected optically. This fluorescence data can be transmitted to a computer which can compute which compounds reacted and the degree of reaction. This technique permits the synthesis and testing of thousands of compounds in days rather than in weeks or even months.
However, the synthesis of each coupling reaction is not always complete, and the yield decreases as the length of the biopolymer increases. The process of aligning a plurality of masks and forming openings in the masks in sequence requires careful alignment and takes time.
The above synthesis is made possible by two other recent technical developments that allow various manipulations and reactions on a planar surface. One is the detection and analysis of DNA fragments and their identification by reaction with specific compounds. Probes, RNA and DNA fragments can be resolved, labeled and detected by high sensitivity sensors. The presence or absence of DNA fragments can identify diseased cells for example.
Another step forward is the ability to separate materials in a microchannel, and the ability to move fluids through such microchannels. This is made possible by use of various electro-kinetic processes such as electrophoresis or electro-osmosis. Fluids may be propelled through very small channels by electro-osmotic forces. An electro-osmotic force is built up in the channel via surface charge buildup by means of an external voltage that can "repel" fluid and cause flow. This surface charge and external voltage produces an electro-kinetic current that results in fluid flow along the channel. Such electro-kinetic processes are the basis for a device described by Pace in U.S. Pat. No. 4,908,112 for example.
Thus real progress has been made using electrophoresis and/or electro-osmosis to move very small amounts of materials along microchannels. Such movement can be used for synthesizing very small samples of potential drug compounds in an array and testing very small amounts of materials for bioactivity. Further progress in fully automating the fluidic processes will result in the synthesis and testing of vast numbers of compounds for bioactivity of all types, which information can be made available for future drug selection and will greatly reduce the time and expense of such testing.